Numerous circuits and devices use microphones for sensing acoustic information such as speech, music, etc. Non-limiting examples of such devices include cellular telephones, digital and tape-based audio recorders, and so on. One general class of microphones utilizes a capacitive membrane. When electrically biased by way of appropriate circuitry, a time-varying electrical charge is present across the capacitive element in accordance with incident acoustic energy. Thus, a capacitive microphone provides an electrical signal representative of the sound energy detected by the microphone.
Capacitive microphones exhibit an undesirably long recovery time when subjected to a “big signal” event, or shock, such as occurs when the microphone is bumped by a solid object, is subjected to an unusually loud sound, etc. This is due to the fact that capacitive microphones and their associated biasing circuitry define an appreciably long time constant (i.e., tau), some being on the order of tens of seconds. A corresponding period of important acoustic information (e.g., speech) can go undetected by the microphone while the capacitive element is re-biased to normal operating signal levels. The slow recovery of capacitive microphones subjected to shock events is undesirable.